1. Field of the Invention
The present invention relates to a lubricating device for an internal combustion engine that incorporates a dry sump type lubricating structure. An oil pump of the present invention incorporates a feed pump and a scavenging pump particularly intended to reduce size and weight dimensions and to offer an increase in pumping capacity.
2. Background Art
A dry sump type oil pump used for an internal combustion engine, including a feed pump and a scavenging pump, has been shown in Japanese Utility Model Laid-open No. Hei 1-179109 and Japanese Patent Laid-open No. Hei 2-9904. The former document discloses a feed pump and a scavenging pump which are separately provided.
Japanese Patent Laid-open No. Hei 2-9904 discloses a dry sump type lubricating device including a feed pump for supplying oil from an oil tank to portions of an engine requiring lubrication, and a scavenging pump for supplying oil that has been used for lubrication and has accumulated on the bottom of the engine to an oil tank. However, in this conventional arrangement, a feed pump and a scavenging pump are separately provided. This device further includes a relief valve provided in a discharge side passage of the feed pump, wherein a discharge port of the relief valve is communicated with a discharge side passage of the scavenging pump via a special passage.
However, since the feed pump and scavenging pump are provided as separate pumps, each of the aforementioned conventional systems suffers from the following shortcomings. First, the required number of parts is correspondingly increased with these conventional systems. In addition, the size and weight of the entire oil system is increased in the conventional systems. Furthermore, the structure and manufacturing process of the oil system is complicated with these conventional systems.
A vehicle running on a rough road or a steep slope, such as a four wheeled buggy or all-terrain vehicle, is often advantageously equipped with dry sump lubrication to ensure a minimum ground clearance and to reduce the center of gravity of the vehicle. However, with the aforementioned types of arrangements, an oil pan's structure must be designed with consideration of the inclination of the vehicular body during operation. This limits the degree of freedom in the design of an oil sump structure such as an oil pan. For example, the oil sump structure cannot be formed into a large irregular shape that potentially reduces clearance under conditions wherein the vehicle is inclined or operated on a steep slope.
This additional consideration results in additional design and manufacturing limitations for the designer. Accordingly, the present invention is aimed at solving the above-described problems.